Best HVAC for a 1,100 sq. ft. passive solar house at 46 N latitude?
We are building high-performance, all electric, 1,100 sq foot passive solar home in cold weather winter climate with hot, humid summers. Slab on grade. Exposed concrete floor as thermal mass. Natural gas is not available. Winter temps infrequently reach -20 to -30 degrees range in December and January. We will use modeling to size heating and cooling system. We will have two bedrooms, open living, dining, and kitchen (primary solar gain area). In addition, there will be a full bath, 1/2 bath, mudroom, and mechanical room. Heating days the last 3 years: 7,065; 8,980; 9,799.
Current HVAC Plan features Mitsubishi variable refrigerant flow (VRF) air source heat pump. Heat pump is effective to -13F. Electric furnace will be used for backup for temps below the heat pump range. Our design team concludes that cabin’s small footprint does not warrant a heat pump with multi-indoor units for zone heating
Instead the design calls for running a single heat pump coil into plenum for electric resistance coil. This plan offers initial cost savings over multi-splits. Duct work will transport heat to individual rooms. We will use a ultra small marine wood stove for backup in case of power failure
Alternate HVAC Plan Utilize efficiency and comfort of being able to control conditions in specific rooms offered by multi-split heat pump. Pros would determine how many indoor units. Electric furnace as backup for temps below the heat pump range
We have a good design team open to suggestions. Subsequently, I welcome your comments or suggestions regarding Current HVAC Plan compared to Alternative HVAC Plan or other alternatives. Thanks.